Method and machine for rotary milling the crankpins and main bearing pins of crankshafts

ABSTRACT

A crankshaft (6) is rotated about its axis (7), and all of its crankpins (28, 29, 30), which each respectively have an eccentricity (e) relative to the axis (7), and all of its main bearing pins (62, 63, 64, 65), which each have non-eccentric cylindrical surfaces, are simultaneously rotary milled by respective first and second allocated rotary milling cutters (34, 35, 36, 70, 71, 72, 73) of a milling cutter set (12). The individual first milling cutters (34, 35, 36) each respectively have an eccentricity (e) corresponding to the eccentricity of the respective crankpin that is to be machined by the respective first milling cutter, while the second milling cutters are non-eccentric circular cutters. The milling cutter set (12) is rotated at the same rotational speed, i.e. with a rotational speed ratio of 1:1, relative to the rotating crankshaft, while simultaneously the milling cutter set is moved in the X-direction toward the crankshaft axis to achieve a feed advance. A rotary milling machine for carrying out the method includes a milling cutter set having the above described first eccentric and second non-eccentric milling cutters, and a drive apparatus for achieving the 1:1 rotation as well as the feed advance motion of the milling cutter set relative to the crankshaft. In this manner, the milling cutters automatically follow the eccentricity of the crankpins, and the non-eccentric rotation of the main bearing pins, without requiring a complicated individual guidance.

PRIORITY CLAIM

This application is based on and claims the priority under 35 U.S.C.§119 of German Patent Application 198 01 863.0, filed on Jan. 20, 1998,the entire disclosure of which is incorporated herein by reference.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to my patent application entitled "METHODAND MACHINE FOR ROTARY MILLING THE CRANKPINS OF CRANKSHAFTS USING DISKMILLING CUTTERS" filed on the same date as the present application.

FIELD OF THE INVENTION

The invention relates to a method for the rotary milling of thecrankpins and main bearing pins of a crankshaft, whereby the crankshaftis held and rotated about its axis in the two chucks of a turningapparatus while the rotary milling is carried out. The invention furtherrelates to a machine for carrying out such a method.

BACKGROUND INFORMATION

Various different methods and apparatus are known for carrying out therotary milling of the crankpins or the main bearing pins of crankshafts.German Patent 195 46 197 (Gesell) discloses a method and an apparatus ofthe above described general type, wherein at least two milling cutterssimultaneously carry out rotary milling or machining on at least twocrankpins of a rotating crankshaft, whereby the crankpins revolve aroundthe axis of the rotating crankshaft. To achieve this, the German Patent195 46 197 discloses a rather complicated guidance of the disk millingcutters to follow the eccentric revolution of the crankpins around thecrankshaft axis as the crankshaft rotates. The reference furthersuggests that the rotation speed of the crankshaft is adapted or variedin view of the optimal milling operation of a rotational tool, and therotational speed of the second and each further rotational tool isregulated dependent on the crankshaft rotational speed prescribed bysuch adaptation or variation. The equipment and method featuresnecessary for carrying out the above mentioned guidance of the diskmilling cutters to follow the motion of the crankpins is regarded asdisadvantageously complicated and costly, and subject to breakdowns andimproper operation.

SUMMARY OF THE INVENTION

In view of the above, it is an object of the invention to provide amethod for the simultaneous rotary milling of a plurality and preferablyall of the crankpins and main bearing pins of a crankshaft, whileavoiding the need for a complicated control and guidance of the diskmilling cutters so as to follow the motion of the crankpins andsimultaneously machine the main bearing pins that do not have aneccentric motion. It is a further object of the invention to provide asimplified machine for carrying out such a method. The invention alsoaims to avoid or overcome the other disadvantages of the prior art, andto achieve additional advantages, as apparent from the presentdescription.

The above objects have been achieved according to the invention in amethod for rotary milling several parts of a workpiece respectivelyhaving different eccentric characteristics, and particularly thecrankpins and main bearing pins of a crankshaft for example, using diskmilling cutters. A plurality and preferably all of the crankpins and themain bearing pins of a crankshaft are respectively rotary milled by acorresponding number of disk milling cutters of a disk milling cutterset. Each disk milling cutter respectively used for milling a givencrankpin has an eccentricity about an axis of the disk milling cutterset that corresponds to the eccentricity of the respective associatedcrankpin about the axis of the crankshaft. On the other hand, each diskmilling cutter respectively used for milling a given main bearing pinhas no eccentricity, i.e. it is arranged with its geometric center onthe rotation axis of the milling cutter set. The entire disk millingcutter set is rotationally driven at the same rotational speed, i.e. ina rotational speed ratio of 1:1, relative to the rotational speed of therotationally driven crankshaft, and is fed or advanced in theX-direction radially toward the rotational axis of the crankshaft.

A machine according to the invention for carrying out the above methodcomprises a machine bed, a turning apparatus mounted on the machine bedand adapted to hold and rotate a crankshaft about its axis, and amilling apparatus mounted on the machine bed and including a diskmilling cutter set including a plurality of first disk milling cuttersrespectively corresponding to or allocated to a plurality of crankpinsand a plurality of second disk milling cutters respectively allocated tothe main bearing pins of the crankshaft that are to be milled. Eachrespective first disk milling cutter allocated to a given crankpin hasthe same eccentricity about the axis of the milling cutter set as therespective allocated crankpin has relative to the rotational axis of thecrankshaft, while each second milling cutter allocated to a given mainbearing pin is arranged without eccentricity relative to the rotationaxis of the milling cutter set. The machine according to the inventionfurther includes a drive apparatus for generating the rotational andfeed advance motion of the disk milling cutter set relative to thecrankshaft, such that the rotational speed ratio between the crankshaftand the disk milling cutter set is 1:1.

In the method and the machine of the invention, since the first millingcutters of the milling cutter set that are used to mill the crankpinseach respectively have the same eccentricity about the axis of themilling cutter set as do the respective plural crankpins about therotational axis of the crankshaft, while the second milling cutters arecircular cutters without eccentricity, and because the milling cutterset rotates at the same rotational speed as the crankshaft during themilling operation, the cutting teeth of the respective first millingcutters automatically or directly follow the eccentric revolving motionof the respectively allocated crankpins that are being milled and thecutting teeth of the second milling cutters follow the non-eccentriccircular rotation of the main bearing pins that are being milled. Inthis manner, it becomes unnecessary to provide a specialized andcomplicated guidance mechanism for the milling cutter set, andparticularly individual guidance means for separately guiding eachindividual milling cutter so as to match the particular motion of itsrespective allocated crankpin or main bearing pin. Instead, theinventive arrangement merely needs to maintain the 1:1 ratio between therotational speeds of the milling cutter set and the crankshaft, whilealso properly carrying out the feed advance of the milling cutter settoward the crankshaft.

In order to adjustably achieve the required eccentricity of each firstdisk milling cutter of the milling cutter set, a preferred embodiment ofthe invention provides that each first disk milling cutter has threeelongated slotted holes arranged therein as follows. One of the slottedholes extends along an elongation direction that extends radiallyrelative to the center of the respective milling cutter, while the othertwo slotted holes extend along elongation directions parallel to that ofthe first slotted hole. Furthermore, the three slotted holes arearranged at locations rotationally offset by substantially 120° fromeach other. With this arrangement, a shifting adjustment of therespective first disk milling cutter along the elongation direction ofthe slotted holes achieves the required adjustable eccentricity of thefirst milling cutter relative to the rotation axis of the cutter set.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be clearly understood, it will now bedescribed in connection with an example embodiment, with reference tothe accompanying drawings, wherein:

FIG. 1 is a general schematic plan view of an apparatus according to theinvention including a rotary milling machine with a disk milling cutterset, as well as a turning apparatus holding a crankshaft that is to bemilled by the milling cutters;

FIG. 2 is an angular sectional view through the milling cutter set andthe crankshaft along the offset section line II--II shown in FIG. 1;

FIG. 3 is a sectional view through the milling cutter set and thecrankshaft along the section line III--III shown in FIG. 1;

FIG. 4 is a sectional view through the milling cutter set and thecrankshaft along the section line IV--IV shown in FIG. 1;

FIG. 5 is a sectional view through the milling cutter set and thecrankshaft along the section line V--V shown in FIG. 1;

FIG. 6 is a sectional view through the milling cutter set and thecrankshaft taken along the section line VI--VI in FIG. 1, on an enlargedscale and in a subsequent operating position in which the milling cutterset and the crankshaft have each respectively rotated 60° furtherrelative to the position shown in FIG. 5;

FIG. 7 is a partially sectioned side view on an enlarged scale, of thecrankshaft that is to be received and machined in the inventiveapparatus, showing the excess material or milling allowance provided onthe crankpins and main bearing pins;

FIG. 8 is an end view of the crankshaft as seen in the direction of thearrow VIII in FIG. 7, showing the respective crankpins in dashed ghostlines behind the counterweight portions of the crankshaft;

FIG. 9 shows a cross-section through the crankshaft taken along thesection line IX--IX in FIG. 7;

FIG. 10 is a geometric diagram illustrating the geometric relationshipspertaining during the rotary milling of a crankpin of a crankshaft, as abasis for calculating the cutting speed components as well as theresultant cutting speed; and

FIG. 11 is a cutting speed diagram representing the cutting speedcomponents and the overall resultant cutting speed in a particularexample machining process for a crankpin of a crankshaft.

DETAILED DESCRIPTION OF PREFERRED EXAMPLE EMBODIMENTS AND OF THE BESTMODE OF THE INVENTION

In the present example, a crankshaft 6 that is to be precision rotarymilled includes three crankpins or connecting rod bearing pins 28, 29and 30 that are respectively rotationally offset by 120° from each otherand that each have an eccentricity or radial offset e relative to therotation axis 7 of the crankshaft 6. The crankshaft 6 further includesmain bearing pins 62, 63, 64 and 65. The crankshaft 6 has previouslybeen cast or otherwise formed into its raw or semi-finished shape, inwhich each crankpin 28, 29 and 30 includes excess material in the formof a machining or milling allowance 31, 32 and 33 that is to be milleddown in the rotary milling operation to a finished crankpin diameter d₂,and each main bearing pin 62, 63, 64, 65 includes a machining allowance66, 67, 68, 69 that is to be milled down to a finished main bearing pindiameter d₁ (see FIGS. 7, 9).

To carry out the milling operation, a rotary milling machine 1 accordingto the invention comprises a machine bed 2 and a turning apparatus 3 aswell as a milling apparatus 3A arranged on the machine bed 2. Theturning apparatus 3 includes two chucks 4 and 5 respectively connectedto and rotationally driven by two drive units 8 and 9, such as arespective driven head stock and tail stock. The crankshaft 6 is mountedin the two chucks 4 and 5 so that the crankshaft 6 can be rotated aboutits axis 7 by operation of the drive units 8 and 9.

In order to be able to receive the crankshaft 6 therebetween, and to beadjustably adaptable to the particular length 10 of the crankshaft, thetwo drive units 8 and 9 are mounted relative to the machine bed 2 insuch a manner so as to be movably adjustable in the direction of theZ-axis, i.e. parallel to the rotation axis 25 of the two drive units,which coincides with the rotation axis 7 of the crankshaft 6. In orderto ensure that the two chucks 4 and 5 rotate at the same speed with thesame rotational force, and thereby to avoid any torsional loading of thecrankshaft 6, an electrical synchronizing circuit or synchronouscontroller C is connected to synchronously drive the two drive units 8and 9. For example, the two drive units respectively comprise separateelectric drive motors, that are synchronously driven through thesynchronous control circuit. Alternatively, the two drive units 8 and 9may be mechanically coupled for a synchronous rotational drive.

The milling apparatus 3A includes a drive apparatus 11 arranged on themachine bed 2 generally next to the turning apparatus 3, as well as adisk milling cutter set 12 received between two spindle boxes 13 and 14.At least the first spindle box 13 is rotationally driven by a motor 15so as to rotationally drive the disk milling cutter set 12 about itsrotation axis 16, which coincides with the rotation axis 26 of the driveapparatus 11. The apparatus is so arranged that the axis 25 of theturning apparatus 3 (coinciding with the rotation axis 7 of thecrankshaft 6) and the rotation axis 26 of the drive apparatus 11(coinciding with the rotation axis 16 of the disk milling cutter set 12)are always parallel to each other lying in a plane 27 extending in theX- and Z-directions between the two axes 25 and 26.

The two spindle boxes 13 and 14 are respectively arranged as movablecarriages on respective double rail guides 17 and 18, and are thussynchronously slidably movable along the guides 17 and 18 in thedirection of the X-axis. This sliding movement of the spindle boxes 13and 14 in a direction of the X-axis causes the milling cutter set 12 tomove toward the crankshaft 6 in a feed advance motion. In order tosynchronously slide the two spindle boxes 13 and 14 in this manner, andthereby achieve the feed advance motion of the milling cutter set 12,two synchronously operating motors 19 and 20 are respectively connectedfor driving the spindle boxes 13 and 14, for example through spindleshafts or the like. The feed advance motion can alternatively beachieved by moving the crankshaft toward the milling cutter set in theX-direction; i.e. it is the relative motion between the milling cutterset and the crankshaft in the X-direction that is significant.

The milling cutter set 12 includes two coupling halves or members 21 and22 at opposite ends thereof, which respectively are coupled to matingcoupling halves 23 and 24 connected to the spindle boxes 13 and 14.Thus, the rotational drive is transmitted from the spindle boxes 13 and14 respectively through the coupling halves 23 and 24 to the couplinghalves 21 and 22 of the milling cutter set 12. Between the two couplinghalves 21 and 22, the milling cutter set 12 further comprises aplurality of (in this example three) first circular milling cutters 34,35 and 36 respectively provided with milling cutter teeth 34', 35' and36' around the circular perimeters thereof and a plurality of (in thisexample four) second circular milling cutters 70, 71, 72 and 73respectively provided with milling cutter teeth 70', 71', 72' and 73'around the circular perimeters thereof. The three first milling cutters34, 35 and 36 may be identical to each other, for example having thesame circular diameter D₂, but are respectively each arranged with adifferent eccentricity relative to the rotation axis 16 of the millingcutter set 12, so as to respectively match the eccentricities e of thecrankpins 28, 29 and 30, as will be described in greater detail below.On the other hand, the four second milling cutters may be identical toeach other, e.g. having the same circular diameter D₁, and are arrangedwithout rotational eccentricity relative to the rotation axis 16 of themilling cutter set 12, as will also be described further below.

In order to carry out the rotary milling operation, the crankshaft 6 isrotated about its axis 7 by the turning apparatus 3, while the millingcutter set 12 is rotated about its axis 16 and moved along the X-axistoward the crankshaft 6. This brings the three first milling cutters 34,35 and 36 respectively into contact with respective allocated ones ofthe crankpins 28, 29 and 30, brings the four second milling cutters 70,71, 72, and 73 respectively into contact with the respective allocatedones of the main bearing pins 62, 63, 64 and 65 and then provides amilling feed advance as the milling progresses. Thereby, the excessmaterial or machining allowance 31, 32 and 33 of the crankpins 28, 29and 30 is milled down to the finished diameter d₂ (see FIG. 9) and themachining allowance 66, 67, 68 and 69 of the main bearing pins 62, 63,64 and 65 is milled down to the finished diameter d₁ (see FIG. 7).

In order to ensure that the milling cutter set 12 matches or follows theeccentricity of the respective crankpins of the crankshaft 6 while alsofollowing the simple circular rotation of the respective main bearingpins of the crankshaft, each respective first milling cutter 34, 35 and36 is set or adjusted to have the same eccentricity e relative to theaxis 16 of the milling cutter set 12, with the same relative rotationaloffset, as the corresponding associated crankpin 28, 29 and 30 hasrelative to the crankshaft axis 7 while each second milling cutter 70,71, 72 and 73 is fixed without eccentricity relative to the rotationaxis 16. Furthermore, the entire milling cutter set 12 is rotated at thesame rotational speed n as the crankshaft 6. This 1:1 rotational speedratio between the crankshaft 6 and the milling cutter set 12 is achievedby a synchronous electrical control of the drive units 8 and 9 of theturning apparatus 3 as well as the motor 15 of the drive apparatus 11,through the synchronous controller C for example. Alternatively, this1:1 rotational speed ratio could be achieved through a mechanical driveconnection, such as a gear train or the like between the turningapparatus 3 and the milling apparatus 3A.

In addition to the three first milling cutters 34, 35 and 36 and foursecond milling cutters 70, 71, 72 and 73, as well as the two couplinghalves 21 and 22, the milling cutter set 12 further comprises sixintermediate spacer disks 74, 75, 76, 77, 78 and 79 respectivelyarranged between adjacent ones of the milling cutters 34, 35, 36, 70,71, 72 and 73, as well as a mounting rod 39. This mounting rod 39includes a centrally arranged shaft 39' and a key or spline 40protruding radially therefrom. The coupling halves 21 and 22, theintermediate spacer disks 74 to 79, and the second milling cutters 70,71, 72 and 73 are mounted on this shaft 39' and secured against rotationon the shaft 39' by the key or spline 40.

Each one of the first milling cutters 34, 35 and 36 allocated formilling the crankpins 28, 29 and 30 is respectively provided with acentral bored hole 41, 42 and 43, having a diameter greater than thetotal resultant diameter of the shaft 39' of the mounting rod 39 withthe key or spline 40 protruding therefrom. Therefore, the three firstmilling cutters 34, 35 and 36 may be passed over the mounting rod 39with free play, so as to remain loose and not fixed relative thereto.The first milling cutters 34, 35 and 36 are secured to the mounting rod39, or actually directly to the intermediate spacer disks 74 to 79, thecoupling halves 21 and 22, and the second milling cutters 70 to 73 aswill be described next.

Each first milling cutter 34, 35 and 36 has three parallel extendingelongated slotted holes 44, 45, 46, or 47, 48, 49, or 50, 51, 52respectively, provided therein. In each one of the first milling cutters34, 35 and 36, a first one of the elongated slotted holes 44, 47, 50extends in its elongation direction radially relative to the respectivemilling cutter center 53, 54 and 55. The two other elongated slottedholes 45 and 46 in the milling cutter 34, or 48 and 49 in the millingcutter 35, or 51 and 52 in the milling cutter 36, respectively extend inelongation directions parallel to the elongation of the first slottedhole 44, 47 or 50 respectively, and are arranged at locations that arerotationally offset substantially by 120° from the first slotted hole44, 47 or 50. This arrangement of the slotted holes can be best seen inFIGS. 3 to 6.

The coupling halves 21 and 22, the intermediate spacer disks 74 to 79,and the second milling cutters 70 to 73 allocated for milling the mainbearing pins 62 to 65 each respectively have the same pattern of aplurality of holes 56 as shown especially in FIG. 2. Of this pluralityof holes 56, three respective holes are brought into alignment ormatching correspondence with the three elongated slotted holes 44 to 52of each respective first milling cutter 34, 35 and 36. The pattern ofplural holes 56 is provided to allow for different adjustments of thefirst milling cutters 34, 35 and 36, or even for the use of differentmilling cutters, to match different eccentric offsets of the crankpinsof different crankshafts that may be machined using the apparatus.

The required eccentricity of the first milling cutters 34, 35 and 36 ina particular case, i.e. for milling a particular crankshaft, is achievedby shifting each respective first milling cutter along the direction ofelongation of the slotted holes 44 to 52 to the required eccentricoffset e of the milling cutter center 53, 54, 55 away from the rotationaxis 16 of the milling cutter set 12 (see FIG. 6). Then the firstmilling cutters 34, 35 and 36 are secured by inserting carrier bolts 57,58 and 59 through the elongated slotted holes 44 to 52 and into orthrough the three respective holes of the hole pattern 56 in each of theintermediate spacer disks, the coupling halves and the second millingcutters that were brought into alignment with the slotted holes 44 to52.

The adjusted eccentricity of each respective milling cutter 34, 35 and36 is thereby fixed by tightening the bolts. Furthermore, as evident inFIGS. 3 to 6, to ensure that each respective milling cutter 34, 35 and36 is absolutely secured or fixed with the proper eccentricity, fillerpieces 60 and 61 are inserted into the respective elongated slottedholes 44 to 52 around the carrier bolts 57, 58 and 59, so that thecross-sectional portion of the carrier bolt together with the fillerpieces 60 and 61 respectively fills out each elongated slotted hole 44to 52 and thereby prevents the milling cutters from sliding or shiftingout of the proper eccentric position. Once the filler pieces 60 and 61are inserted and the bolts 57, 58 and 59 are tightened, they also serveto rotationally drive or carry the first milling cutters 34, 35 and 36along with the coupling halves 21 and 22, the intermediate spacer disks74 to 79, and the second milling cutters 70 to 73, which arerotationally driven by the mounting rod 39 through the key or spline 40.

The rotary milling machine 1 is used to carry out the milling ormachining of the crankpins 28, 29 and 30 and the main bearing pins 62 to65 by means of countermilling, i.e. the milling cutter set 12 and thecrankshaft 6 rotate in opposite or counter-directions (see e.g. FIG. 6),with the same rotational speed n. During the rotary milling of the mainbearing pins 62 to 65, the motion of second milling cutters 70 to 73provides a first cutting speed component v_(FHL), and the motion of themain bearing pins 62 to 65 provides a second cutting speed componentv_(HL), whereby these two cutting speed components v_(FHL) and v_(HL)together give the overall resultant cutting speed v_(RHL) of the cuttingteeth of the second milling cutters relative to the surface of the mainbearing pins being milled. Since the main bearing pins 62 to 65 and thesecond milling cutters 70 to 73 simply rotate circularly withouteccentricity, each of the cutting speed components v_(HL) and v_(FHL) aswell as the total resultant cutting speed v_(RHL) for the main bearingpins remains always constant. The formulas applicable for calculatingthe cutting speed in this context are as follows.

    v.sub.FHL =π·n·D.sub.1

    v.sub.HL =π·n·d.sub.1

    v.sub.RHL =v.sub.FHL +v.sub.HL =π·n·(D.sub.1 +d.sub.1)

During the rotary milling of the crankpins 28, 29 and 30, the motion ofthe first milling cutters 34, 35 and 36 provides a first cutting speedcomponent v_(FPL) and the motion of the crankpins 28, 29 and 30 providesa second cutting speed component v_(PL), whereby these two cutting speedcomponents together give the overall resultant cutting speed v_(RPL) ofthe cutting teeth of the first milling cutters relative to the surfaceof the crankpins being milled. Since the crankpins 28, 29 and 30 and thefirst cutters 34, 35 and 36 revolve eccentrically, the cutting speedcomponents v_(FPL) and v_(PL) are not constant.

The geometric diagram shown in FIG. 10 illustrates the derivation of thefollowing formulas that can be used for calculating the cutting speedcomponents v_(FPL) and v_(PL) and the resultant cutting speed v_(RPL) inthe context of milling the crankpins. ##EQU1##

The cutting speed diagram shown in FIG. 11 illustrates the cutting speedcomponents and the resultant cutting speed relating to machining of thecrankpins, over a rotational angular range of φ=0 to 2π. The resultantcutting speeds v_(RHL) and v_(RPL) for the main bearing pins and for thecrankpins respectively, may be calculated for the following machiningprocess parameters:

D₁ =990 mm=diameter of each second milling cutter 70-73;

d₁ =50 mm=diameter of each main bearing pin 62 to 65;

D₂ =1000 mm=diameter of each first milling cutter 34, 35, 36 (D₂ =2R);

d₂ =40 mm=diameter of each crankpin 28, 29 30 (d₂ =2r);

e=30 mm=eccentricity of a crankpin 28, 29, 30;

n=60/min.=rotational speed of the crankshaft 6 and of the milling cutterset 12.

Using the above parameter values, it is possible to calculate theresultant cutting speed v_(RHL) that remains constant at all times, andthe resultant cutting speed v_(RPL) in the machining positions shown inFIGS. 6 and 3, as follows.

    v.sub.RHL =π·n·(D.sub.1 +d.sub.1)

    v.sub.RHL =π·60·(0.990+0.050)

    v.sub.RHL =196.11 m/min ##EQU2##

Along the lines of the calculations above, also for the machiningpositions of the crankpins 28, 29, 30 between φ=0 to π and φ=π to 2π,the resultant cutting speed v_(RPL) is always constant at 196.11 m/min.Thus, v_(RPL) is always equal to v_(RHL), which leads to uniformconstant cutting conditions for both the main bearing pins and thecrankpins.

At the beginning of the machining process, the resultant cutting speedsv_(RPL) and v_(RHL) are slightly higher due to the influence of theexcess material in the form of the machining allowances 31, 32, 33, 66,67, 68 and 69 which slightly increase the radius of the outer surfacesof the crankpins 28, 29 and 30 and the main bearing pins 62 to 65 asshown in FIG. 7. For example, if a radial enlargement of 3 mm is takeninto account for the machining allowances 31, 32, 33, 66, 67, 68 and 69,the resultant cutting speeds v_(RPL) and v_(RHL) are each determined as196.11+(2·π·60·0.003)=196.11+1.13=197.24 m/min.

Although the invention has been described with reference to specificexample embodiments, it will be appreciated that it is intended to coverall modifications and equivalents within the scope of the appendedclaims. It should also be understood that the present disclosureincludes all possible combinations of any individual features recited inany of the appended claims.

What is claimed is:
 1. A method of rotary milling a plurality of partsof a workpiece, wherein first ones of said parts respectively have firsteccentricities relative to a first rotation axis of said workpiece andsecond ones of said parts respectively have a regular circular contourwithout eccentricity relative to said first rotation axis, said methodcomprising the following steps:a) providing a milling cutter setcomprising a plurality of first milling cutters respectively allocatedfor milling respective ones of said first parts of said workpiece and aplurality of second milling cutters respectively allocated for millingrespective ones of said second parts of said workpiece, wherein saidfirst milling cutters respectively have second eccentricities relativeto a second rotation axis of said milling cutter set, and wherein saidsecond eccentricities of said first milling cutters respectivelycorrespond to said first eccentricities of said first parts of saidworkpiece to which said first milling cutters are respectivelyallocated; b) rotating said workpiece about said first rotation axis ata first rotational speed; c) rotating said milling cutter set about saidsecond rotation axis at a second rotational speed matching said firstrotational speed in a 1:1 ratio; and d) relatively moving said millingcutter set in a direction radially toward said workpiece so as to bringsaid milling cutters respectively into contact with respective allocatedones of said parts of said workpiece and to achieve a milling feedadvance of said milling cutters relative to said workpiece.
 2. Themethod according to claim 1, wherein said workpiece is a crankshaft,said first parts of said workpiece are crankpins of said crankshaft, andsaid second parts of said workpiece are main bearing pins of saidcrankshaft.
 3. The method according to claim 2, wherein said pluralityof first parts includes all of said crankpins of said crankshaft andsaid plurality of second parts includes all of said main bearing pins ofsaid crankshaft, and further comprising carrying out said steps a), b),c) and d) so as to simultaneously mill all of said crankpins and all ofsaid main bearing pins of said crankshaft.
 4. The method according toclaim 2, wherein said main bearing pins are arranged concentrically andwithout eccentricity relative to said first rotation axis of saidcrankshaft, and said second milling cutters are circular cuttersarranged concentrically and without eccentricity relative to said secondrotation axis of said milling cutter set.
 5. The method according toclaim 1, wherein each one of said second eccentricities is respectivelydefined by a radial distance offset and by a rotational angle of ageometric center of a respective one of said first milling cuttersrelative to said second rotation axis, and wherein said secondeccentricities all comprise the same said radial distance offset anddifferent ones of said rotational angle uniformly rotationallydistributed around said second rotation axis.
 6. The method according toclaim 1, wherein said workpiece is rotated about said first rotationaxis and said milling cutter set is rotated about said second rotationaxis in respective opposite rotation directions.
 7. The method accordingto claim 1, wherein said steps are carried out such that a resultantcutting speed of cutting tips of said milling cutters relative to asurface being milled of said parts of said workpiece remainssubstantially constant during a complete rotation of said workpiece, andsaid resultant cutting speed of said first milling cutters is alwaysequal to said resultant cutting speed of said second milling cutters. 8.The method according to claim 1, wherein said step a) further comprisesfixing together said milling cutters to prevent relative rotationtherebetween, so that all of said milling cutters in said milling cutterset rotate in unison as a single unit in said step c).
 9. A machine forrotary milling a plurality of parts of a workpiece, wherein first onesof said parts respectively have first eccentricities relative to a firstrotation axis of said workpiece and second ones of said partsrespectively have a regular circular contour without eccentricityrelative to said first rotation axis, said machine comprising:a turningapparatus adapted to receive and hold said workpiece and to rotate saidworkpiece about said first rotation axis at a first rotational speed; amilling apparatus comprising a milling cutter set, and a drive apparatusconnected to said milling cutter set; and a synchronous speed controllerconnected to control said drive apparatus and said turning apparatus;wherein said milling cutter set comprises a plurality of first millingcutters respectively allocated for milling respective ones of said firstparts of said workpiece and a plurality of second milling cuttersrespectively allocated for milling respective ones of said second partsof said workpiece, wherein said first milling cutters respectively havesecond eccentricities relative to a second rotation axis of said millingcutter set, and wherein said second eccentricities of said first millingcutters respectively correspond to said first eccentricities of saidfirst parts of said workpiece to which said first milling cutters arerespectively allocated; wherein said drive apparatus is connected tosaid milling cutter set so as to rotate said milling cutter set aboutsaid second rotation axis at a second rotational speed and totranslationally move said milling cutter set relative to said turningapparatus in a direction extending radially relative to said firstrotation axis of said workpiece; and wherein said synchronous speedcontroller is connected to said drive apparatus and to said turningapparatus and is adapted to control said drive apparatus and saidturning apparatus to establish a 1:1 ratio between said first rotationalspeed and said second rotational speed.
 10. The machine according toclaim 9, wherein said drive apparatus comprises a spindle box, a firstdrive motor connected through said spindle box to said milling cutterset so as to rotationally drive said milling cutter set, and a seconddrive motor connected to said spindle box so as to translationally movesaid spindle box and said milling cutter set relative to said turningapparatus while keeping said second rotation axis parallel to said firstrotation axis.
 11. The machine according to claim 10, wherein saidturning apparatus comprises two chucks adapted to receive opposite endsof said workpiece, and two motors that are driven synchronously witheach other and that are respectively connected to said two chucks. 12.The machine according to claim 9, wherein said milling cutter setfurther comprises a mounting rod, coupling members arranged at oppositeends of said mounting rod, and a respective intermediate spacer diskinterposed between each two adjacent ones of said milling cutters,wherein said coupling members are connected to said drive apparatus. 13.The machine according to claim 12, wherein said mounting rod includes ashaft and an interlocking key protruding radially outwardly from saidshaft, each said spacer disk has a first hole therethrough fitting onsaid mounting rod with a notch in said first hole receiving and engagingsaid key so as to fix said spacer disk against rotation relative to saidmounting rod, each said second milling cutter has a second holetherethrough fitting on said mounting rod with a notch in said secondhole receiving and engaging said key so as to fix said second millingcutter against rotation relative to said mounting rod, and each saidfirst milling cutter has a third hole therethrough with a diametersufficiently large to pass said mounting rod including said key throughsaid third hole with free play clearance.
 14. The machine according toclaim 12, wherein each said first milling cutter has therein threeelongated slotted holes, which respectively extend in mutually parallelelongation directions, and which include a first slotted hole of whichsaid elongation direction extends radially relative to a geometriccenter of said respective first milling cutter and two further slottedholes arranged at locations rotationally spaced respectively by 120°relative to said first slotted hole.
 15. The machine according to claim14, wherein each one of said coupling members, each said intermediatespacer disk, and each one of said second milling cutters respectivelyhas a same pattern of a plurality of mounting holes therein, includingthree mounting holes that are respectively in alignment through eachsaid coupling member, each said spacer disk, and each said secondmilling cutter, and that are respectively in overlapping alignment withsaid three elongated slotted holes of each said first milling cutter.16. The machine according to claim 15, wherein said secondeccentricities are determined for a respective one of said first millingcutters by a sliding position of said respective first milling cutteralong said mutually parallel elongation directions of said slotted holesin variable overlapping alignment with said three mounting holes, andwith said geometric center of said respective first milling cuttereccentrically offset from said second rotation axis of said millingcutter set.
 17. The machine according to claim 15, further comprisingthree carrier bolts extending through said three elongated slotted holesof said first milling cutters and through said three mounting holes ofeach said coupling member, each said intermediate spacer disk, and eachsaid second milling cutter, so as to interconnect said milling cutters,each said spacer disk, and said coupling members.
 18. The machineaccording to claim 17, further comprising two filler pieces respectivelyinserted into each said elongated slotted hole of each said firstmilling cutter together with and adjacent to a respective one of saidcarrier bolts.
 19. The machine according to claim 15, wherein saidpattern of a plurality of mounting holes includes more holes than saidthree mounting holes.
 20. The machine according to claim 9, wherein eachof said first milling cutters is identical to the others of said firstmilling cutters.